Large femtosecond two-photon absorption cross sections of fullerosome vesicle nanostructures derived from a highly photoresponsive amphiphilic C 60-light-harvesting fluorene dyad

Abstract

We demonstrated ultrafast femtosecond nonlinear optical (NLO) absorption characteristics of bilayered fullerosome vesicle nanostructures derived from molecular self-assembly of amphiphilic oligo(ethylene glycolated) C 60-(light-harvesting diphenylaminofluorene antenna). Fullerene conjugates were designed to enhance photoresponse in a femtosecond time scale by applying an isomerizable periconjugation linker between the C60 cage and a diphenylaminofluorene antenna subunit in an intramolecular contact distance of only DPAF-EG 12C1)-based fullerosome nanovesicles in H2O was characterized to consist of a bilayered shell with a sphere diameter of 20-70 nm and a chromophore shell width of 9.0-10 nm, fitting well with a head-to-head packing configuration of the molecular length. At the estimated effective nanovesicle concentration as low as 5.5 × 10-8 MV (molecular molar concentration of 5.0 × 10-4 M) in H2O, two-photon absorption (2PA) phenomena were found to be the dominating photophysical events showing a large molar concentration-insensitive 2PA cross-section value equivalent to 8500 GM in a form of nanovesicles, on average. The observed NLO characteristics led to a sharp trend of efficient light-transmittance intensity reduction at the input laser intensity above 100 GW/cm2. © 2011 American Chemical Society.